Dielectric Film, Associated Article and Method

ABSTRACT

An article having a cyanoresin dielectric film is described. The cyanoresin dielectric film includes nanostructures of a toughening material. A method of forming such a cyanoresin dielectric film is also described. A capacitor having a cyanoresin dielectric film is presented.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH AND DEVELOPMENT

This invention was made with Government support under contract numberFA9451-08-C-0166, awarded by the Defense Advanced Research ProjectsAgency (DARPA), U.S. Department of Defense. The Government has certainrights in the invention.

BACKGROUND

The invention relates generally to high energy density capacitors, andmore particularly, to such capacitors incorporating a thin film of apolymer having a high dielectric constant and high breakdown strength.The invention further relates to a method of manufacturing suchdielectric thin films, and to a capacitor comprising the same.

High energy density capacitors have become increasingly important invarious industrial, military, and commercial operations. Polymer basedcapacitors are lightweight and compact and hence, are attractive forvarious land based and space applications. However, most of thedielectric polymers are characterized by low energy densities (<5 J/cc),and have low breakdown strength (<450 kV/mm), which may limit theoperating voltage of the capacitor. In order to achieve high energydensity, it may be desirable to have both high dielectric constantcharacteristics, and high breakdown strength. A trade-off between thesetwo properties may not be advantageous.

Most of the dielectric polymers that exhibit high breakdown strengthhave a low dielectric constant. Typically, high dielectric-constantceramic fillers are used to increase the dielectric constant of thepolymer. Further increases in the dielectric constant of the polymer canbe achieved by including a high concentration of the ceramic filler. Forexample, the polymer-ceramic composite with a dielectric constant equalto 150 has a ceramic filler loading density as high as 85% by volume,which is about 98% by weight. However, a high concentration of theceramic filler not only decreases the mechanical flexibility of thecomposite, but also introduces interfacial defects and thus, lowers thebreakdown strength of the composites.

The cyanoresin family of polymers have high dielectric constants (∈>15),and are commercially available as film forming resins. Commercial-grade,high dielectric-constant cyanoresins have been available and widely usedas coating materials for electroluminescent lamps. However, cyanoresinsusually do not have enough mechanical strength to be processed intofree-standing films for capacitor fabrication. Usually, the film cracks,due to embrittlement of the material.

The breakdown strength of some of these films has been reported to bebelow 200 kV/mm. These resins have been studied and processed for highquality films with high breakdown strength. However, pure cyanoresinfilms such as CR-C (cyanoethyl cellulose) and CR-E (cyanoethylhydroxyethyl cellulose) are reported to be highly brittle. Hence, theyare conventionally used only as blends with other polymers. CR-S(cyanoethyl pullulan) is another suitable polymer in terms of propertiesand processing.

Thus, there is a need to improve the toughness of cyanoresins withoutcompromising their dielectric properties. It is also desirable to have acyanoresin film having a high dielectric constant and a high breakdownstrength, with improved mechanical strength over currently existingdielectric films.

BRIEF DESCRIPTION

Some embodiments of the invention provide an article including acyanoresin dielectric film. The cyanoresin dielectric film includesnanostructures of a toughening material.

According to some embodiments of the invention, a capacitor is provided.The capacitor includes a cyanoresin dielectric film and at least oneelectrode coupled to the cyanoresin dielectric film. The cyanoresindielectric film includes nanostructures of a toughening material.

In some embodiments, a method of forming a dielectric film is provided.The method includes the steps of dissolving a cyanoresin in a solvent toform a solution, and dispersing a toughening material in the solution.The method further includes the step of applying the solution to asubstrate to form the dielectric film. The cyanoresin dielectric filmincludes nanostructures of the toughening material.

DRAWINGS

These and other features, aspects, and advantages of the presentinvention will become better understood when the following detaileddescription is read with reference to the accompanying drawings in whichlike characters represent like parts throughout the drawings, wherein:

FIG. 1 is a schematic representation of chemical structures ofcyanoresins, according to one embodiment of the invention;

FIG. 2 illustrates a capacitor, according to one embodiment of theinvention;

FIG. 3 is a flow chart of a method of forming a cyanoresin dielectricfilm, according to one embodiment of the invention;

FIG. 4 is a transmission electron micrograph of a cyanoresin dielectricfilm, according to one embodiment of the invention.

DETAILED DESCRIPTION

Approximating language, as used herein throughout the specification andclaims, may be applied to modify any quantitative representation thatcould permissibly vary without resulting in a change in the basicfunction to which it is related. Accordingly, a value modified by a termor terms, such as “about,” is not limited to the precise valuespecified. In some instances, the approximating language may correspondto the precision of an instrument for measuring the value.

In the following specification and claims, the singular forms “a”, “an”and “the” include plural referents unless the context clearly dictatesotherwise.

As used herein, the terms “may” and “may be” indicate a possibility ofan occurrence within a set of circumstances; a possession of a specifiedproperty, characteristic or function; and/or qualify another verb byexpressing one or more of an ability, capability, or possibilityassociated with the qualified verb. Accordingly, usage of “may” and “maybe” indicates that a modified term is apparently appropriate, capable,or suitable for an indicated capacity, function, or usage, while takinginto account that in some circumstances the modified term may sometimesnot be appropriate, capable, or suitable. For example, in somecircumstances, an event or capacity can be expected, while in othercircumstances the event or capacity cannot occur—this distinction iscaptured by the terms “may” and “may be”.

Some of the dielectric properties considered herein are the dielectricconstant, the dielectric breakdown voltage or dielectric breakdownstrength, and the energy density. The “dielectric constant” of adielectric material is a ratio of the capacitance of a capacitor, inwhich the space between and around the electrodes is filled with thedielectric material, to the capacitance of the same configuration ofelectrodes in a vacuum. As used herein, “dielectric breakdown strength”refers to a measure of the dielectric breakdown resistance of a polymercomposite (dielectric) material under an applied AC or DC voltage. Theapplied voltage prior to breakdown is divided by the thickness of thedielectric (polymer) material, to provide the breakdown strength valueor breakdown voltage. It is generally measured in units of potentialdifference over units of length, such as kilovolts per millimeter(kV/mm).

The energy of a capacitor is generally calculated by the equation E=(½)CV², where C is the capacitance in farads (F), and V is the workingvoltage of the capacitor in volts (V). These relationships may also beexpressed as a function of the electric field, E. If the dielectricconstant K of the material does not change with the applied electricfield E (in V/um), the electric energy density U_(E) (in J/cc) stored ina capacitor can be calculated by

U _(E)=½∈₀ KE ²,

where ∈₀ is the permittivity of vacuum. The highest electric field thatcan be applied to a material is called its dielectric breakdownstrength. As used herein, the term “high temperatures” refers totemperatures above about 100 degrees Celsius (° C.), unless otherwiseindicated.

According to one embodiment of the invention, an article including acyanoresin dielectric film is provided. The cyanoresin dielectric filmincludes nanostructures of a toughening material. As used herein,“toughening material” refers to an additive material, which increasesmechanical strength of a base material (the cyanoresin) at least byabout 5%.

The dielectric film or layer is not limited to specific cyanoresins.Examples of suitable cyanoresins include, but are not limited to,cyanoethyl pullulan (CR-S resin), cyanoethyl polyvinylalcohol,cyanoethyl hydroxyethyl cellulose (CR-E), and cyanoethyl cellulose (CR-Cresin). In one exemplary embodiment, the cyanoresin includes cyanoethylcellulose. In another embodiment, the cyanoresin includes cyanoethylpullulan. The structures of the repeating unit of the cyanoresins, foruse in certain embodiments of the invention, are provided in FIG. 1.Schematic 10 shows the repeating unit of a CR-S resin, and schematic 12shows the repeat units of a CR-C resin—where R is —CH₂—CH₂—CN or H. Asufficient amount of the cyano group should be present to provide thedesired nitrogen content. In the formula corresponding to schematic 12,each of the pendent CH₂OR groups, individually, can alternatively be aCH₂OR′ group, wherein R′ is —CH₂—CH₂—OH or H. In some embodiments, ablend of cyanoresins may be used for the dielectric film.

The cyanoresins may have an aliphatic, aromatic or an aryloxy backbone.The cyanoresins have a nitrogen content based on CN groups. In certainembodiments, the nitrogen content is about 7% to about 15% by weight. Inother embodiments, the nitrogen content is about 9% to about 13% byweight. The cyanoresins are usually characterized by a viscosity (20%N,N-dimethylformamide or DMF, solution at 20° C.) from about 100centipoises (cP) to about 1000 cP. The CN group has a substantially highdipole moment and a substantially high mobility to reorient underelectric fields, and may lead to a high dielectric constant. The CR-Sresin has a dielectric constant of 19.5, and the CR-C resin has adielectric constant of 16.5 at room temperature. The high dielectricconstant of the cyanoresin, combined with its high breakdown strength,may facilitate high energy density.

The cyanoresin includes an effective amount of a toughening material. Aprimary purpose of the toughening material is to improve the toughnessof cyanoresins for thin film formation. However, the specific tougheningmaterial, and its level, are selected to improve the mechanicalstrength, such as tensile strength of cyanoresins for film formation,and to maintain the dielectric properties of the cyanoresins.

Suitable toughening materials may include thermoplastic polymers.Non-limiting examples include acrylate block copolymers, aromaticpolyimides, siloxane and imide block copolymers and the like. Thearomatic polyimides are usually prepared from poly(amic acids). Aromaticpolyimides are usually synthesized from aromatic dianhydrides andaromatic diamines. Examples of aromatic dianhydrides include, but arenot limited to, benzophenone tetracarboxylic dianhydride (BTDA),Bisphenol A dianhydride, oxydiphthalic anhydride, and pyromelliticdianhydride. Examples of aromatic diamines include, but are not limitedto, oxydianiline (ODA), phenylenediamine (PDA), bis-aminophenoxybenzene,and bis(aminophenoxy phenyl)propane.

Acrylate block copolymers usually include an ABA or ABC acrylate blockconfiguration. A, B and C are each monomers blocks, and ABA or ABCrepresents a repeating unit in the acrylate block copolymer. Suitableexamples of A include, but are not limited to, poly(methylmethacrylate). Suitable examples of B include, but are not limited to,polysiloxanes and polybutylacrylate/polybutadiene. Non-limiting examplesof C include polystyrene.

In an exemplary embodiment, the repeating unit of the ABA acrylate blockcopolymer is PMMA-PBA-PMMA, wherein “PMMA” is poly(methyl methacrylate;and “PBA” is poly(butyl acrylate). In another exemplary embodiment, therepeating unit of an ABC acrylate block copolymer is PS-PBd-PMMA,wherein “PS” is polystyrene, “PBd” is polybutadiene, and “PMMA” ispoly(methyl methacrylate. In a preferred embodiment, the acrylate blockcopolymers are ABA block copolymers, M22 and M22N (from Arkema, Inc.),and siloxane polyetherimide block copolymers (STM1700 from SABICInnovative Plastics).

The most appropriate amount of the toughening material is usuallydetermined by the application in which the material is being used, aswell as the identity of the particular toughener. An “effective amount”of the toughening material is an amount sufficient to improve thetoughness of the cyanoresin film, without significantly compromising itsdielectric properties. Embodiments of the present invention may utilizecyanoresins containing at least about 10% by weight of the tougheningmaterial. Preferably, the toughening material (i.e., toughener) ispresent in an amount of about 10% to about 20% by weight.

Moreover, for embodiments of this invention, the toughening material ispresent in cyanoresins in the form of nanostructures. As used herein,the term “nanostructure” is meant to describe a structure having atleast one region or characteristic dimension with a feature size of lessthan about 500 nanometers (nm), less than about 200 nm, less than about100 nm, less than about 50 nm, or even less than about 20 nm. Examplesof such structures include nanowires, nanorods, nanotubes, branchednanocrystals, nanotetrapods, tripods, bipods, nanocrystals, nanodots,nanoparticles and the like. Nanostructures can be substantiallyhomogeneous in material properties. However, in other embodiments, thenanostructures can be heterogeneous. Nanostructures can be substantiallycrystalline (monocrystalline or polycrystalline), amorphous, or acombination thereof. Other features of the nanostructure can have a sizein the micrometer or even millimeter range. In one aspect, at least onedimension of the nanostructure has a size less than about 500 nm, forexample, less than about 200 nm, less than about 100 nm, less than about50 nm, or even less than about 20 nm.

In certain embodiments, the cyanoresin dielectric film has a thicknessin a range from about 0.1 micron to about 50 microns. In a particularembodiment, the dielectric film has a thickness in a range from about0.1 micron to about 10 microns. As will be discussed in detail below,the dielectric breakdown strength of the dielectric film was found to beinversely proportional to the film thickness. Accordingly, the selectedthickness of the dielectric film is, in part, dependent on the requiredenergy density, and the processing feasibility. In certain embodiments,the dielectric films may have higher film thicknesses, for example, in arange from about 3 microns to about 50 microns.

In specific embodiments, filler particles are dispersed in thecyanoresin matrix. The filler particles may contribute positivelytowards the dielectric constant of the film, and hence may beadvantageously utilized. These filler particles have been found toincrease the dielectric constant and hence, the energy storage capacity,while maintaining all other high performance parameters, such as highresistivity, low dissipation factor, and high breakdown voltage.

In one embodiment, the filler particles comprise a ceramic material. Theceramic particles may be ferroelectric or antiferroelectric particles.The ferroelectric and antiferroelectric effect is an electricalphenomenon whereby certain ionic crystals may exhibit a spontaneousdipole moment. Examples of suitable ceramics include, but are notlimited to, alumina, titania, zirconia, magnesia, zinc oxide, cesiumoxide, yttria, silica, barium titanate, strontium titanate, leadzirconate, lead zirconium titanate, and various combinations of these.In one embodiment, preferred filler particles are antiferroelectricparticles.

The antiferroelectric particles can be converted to ferroelectricparticles upon the application of an electric field. Thus, theantiferroelectric particles are usually field-tunable, non-lineardielectric particles that can undergo a phase transition from a lowdielectric state (antiferroelectric state) to a high dielectric state(ferroelectric state) upon being exposed to an electric field. A biasingelectric field of less than or equal to about 100 kilovolts/millimeteris generally used to change the state of the antiferroelectric particles(from the antiferroelectric state to the ferroelectric state) that areincorporated into the cyanoresin. This biasing electric field can beaccompanied by the application of heat to a sample. Heat may be appliedin the form of convection, conduction or radiation to the sample duringthe application of the biasing electrical field.

The electric field aligns the filler particles into a columnar structureso as to give rise to a higher dielectric constant. Suchantiferroelectric particles and their effect on dielectric properties ofa polymer are described in a patent application (Publication No. US20070117913A1) entitled “Antiferroelectric Polymer Composites, Methodsof Manufacture Thereof, And Articles Comprising the Same” filed on Nov.23, 2005, which is incorporated herein by reference.

The filler particles are usually characterized by a mean particle sizein a range from about 5 nanometers to about 500 nanometers. In oneembodiment, the mean particle size is in a range from about 10nanometers to about 100 nanometers. The filler particles are present atan appropriate amount, depending on some of the factors mentionedpreviously. Typically, the amount of the filler particles is less thanabout 60 weight percent of the weight of the cyanoresin. In oneembodiment, the amount of the filler particles is in a range from about0.1 weight percent to about 30 weight percent of the cyanoresin. In oneembodiment, the amount of the filler particles is in a range from about0.1 weight percent to about 20 weight percent of the cyanoresin. Theparticle size and the weight percent of filler particles may affect thefilm forming capability and hence, may be optimized appropriately.

The dielectric breakdown strength of the dielectric film may be in partcontrolled by the film composition, film thickness, and the quality ofthe film—usually defined by surface defects, film deposition, andsurface chemical modification. Typically, for general embodiments of theinvention, the dielectric film has a breakdown strength of at leastabout 200 kV/mm. In one embodiment, the dielectric film has a breakdownstrength in a range from about 200 kV/mm to about 1000 kV/mm. In somepreferred embodiments, the dielectric film has a breakdown strength in arange from about 300 kV/mm to about 700 kV/mm.

Thinner dielectric films usually exhibit higher breakdown strengthvalues (the breakdown strength of the dielectric film can be improved byreducing the thickness of the film). The toughened dielectric films havegood mechanical strength, and can be processed into freestanding films,even of reduced thickness. For example, a CRC film with 20 weight % oftoughening material M22 (discussed above), and having a thickness of 15microns, has shown a breakdown strength value of 400 kV/mm. Reduction offilm thickness to 5.5 microns has been achieved with an improvedbreakdown strength of 570 kV/mm, respectively.

In one embodiment, the dielectric constant of the cyanoresin dielectricfilm may be in a range from about 10 to about 50. In another embodiment,the dielectric constant of the cyanoresin dielectric film may be in arange from about 10 to about 30. Moreover, in one embodiment, thecyanoresin dielectric film has a dissipation factor in a range fromabout 0.01 to about 0.1 at 1 kHz.

Embodiments of the present invention provide a capacitor, including adielectric film and at least one electrode coupled to the dielectricfilm. FIG. 2 provides a simplified illustration of a capacitor 20,having a dielectric film 22 deposited on a substrate 24. The dielectricfilm 22 includes a cyanoresin. The cyanoresin dielectric film includesnanostructures of a toughening material. An electrode 26 is coupled tothe dielectric film 22. Typically, the electrode 26 may include a layerof a conducting polymer or a metal. Commonly used metals includealuminum, stainless steel, titanium, zinc and copper. The electrodelayer is typically thin, in the order of from about 50 Å to about 500 Å.In some embodiments, the capacitor may be a multilayer capacitor. Insuch embodiments, a number of dielectric films and electrode layers arealternately arranged to form a multilayer capacitor.

Substantially high dielectric constant values, and high breakdownstrength values for the films, facilitate high-energy storage for thecapacitors. In one embodiment, the energy density of the capacitor is atleast about 5 J/cubic centimeters. In another embodiment, the energydensity of the capacitor is at least about 10 J/cc. In yet anotherembodiment, the energy density of the capacitor is at least about 20J/cc.

The capacitor may optionally include a capping layer disposed on thedielectric film. Examples of suitable capping layer materials include,but are not limited to, polycarbonate, cellulose acetate,polyetherimide, fluoropolymer, parylene, acrylate, silicon oxide,silicon nitride, and polyvinylidene fluoride. For particularembodiments, the capping layer has a thickness of less than about 10% ofthe thickness of the dielectric film. The capping layer may help infilling in or otherwise mitigating surface defects and hence, mayimprove the breakdown strength of the film. It should also be emphasizedthat the present invention is not limited to any particular type ofcapacitor, as long as the features described herein are present.

Embodiments of the present invention further provide a method 30 offorming a cyanoresin dielectric film, as illustrated in flow chart ofFIG. 3. The method 30 includes the steps of dissolving a cyanoresin in asolvent to form a solution, step 32; dispersing a toughening material inthe solution, step 34; and applying the solution to a substrate to formthe dielectric film, step 38. The method may include an additional,optional step 36 of dispersing filler particles in the solution, priorto performing the step 38.

In step 32, the cyanoresin is dissolved in any suitable solvent. Inparticular embodiments, the solvent is selected from the groupconsisting of acetone, acetonitrile, cyclohexanone, furfuryl alcohol,tetrahydrofurfuryl alcohol, methyl acetoacetate, nitromethane,N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP),butyrolactone, propylene carbonate, and various combinations of these.In an exemplary embodiment, the solvent comprises N,N-dimethylformamide.

In step 34, the toughening material is dispersed in the solution by asuitable dispersion method. Examples of suitable dispersion techniquesinclude, but are not limited to, melt-dispersion and solvent-dispersion.These dispersion techniques may also use additional energy, such asshear, compression, ultrasonic vibration, or the like, to promotehomogenization of the toughening nanostructures with the cyanoresin. Inone embodiment, a cyanoresin suspended in a fluid (e.g., a solvent) maybe introduced into an ultrasonic sonicator along with the tougheningnanostructures. The mixture may be solution-blended by sonication, for atime period effective to disperse the nanostructures within thecyanoresin and the fluid.

In some embodiments, the method 30 optionally includes a step 36 ofdispersing filler particles in the solution prior to applying thesolution to a substrate, step 38. The filler particles may also bedispersed within the cyanoresin along with or after dispersing thetoughening material by the same dispersion techniques as discussedabove.

The solution of the cyanoresin is applied to a substrate by any suitableprocess known in the art, in step 38. Examples of suitable coatingprocesses include, but are not limited to, tape-casting, dip coating,spin coating, chemical vapor deposition, melt extrusion, and physicalvapor deposition, such as sputtering. Typically, the dielectric film hasa thickness of less than about 5 microns. In one preferred embodiment,the film may be applied by a tape-casting process. When the filmthickness is substantially small, solution based coating techniques suchas spin coating or dip coating may be used. In an exemplary embodiment,the film may be preferably applied by a spin coating process.

During film formation in the coating process, the molecular tougheningmaterial segregates from the cyanoresin and self-assembles intonanosized or microsized domains or nano structures. This segregation ofthe toughening material occurs due to interaction between the cyanogroup and the toughening material. Those skilled in the art would beable to control the interaction between the cyano group and thetoughening material and, thus, the characteristic dimension of thenanostructures by adjusting processing conditions, such as temperature,and the concentration of the toughening material and the cyanoresin inthe solution. It should be understood that the dimension of thenanostructures varies with processing conditions.

In some embodiments, the nanostructures have a characteristic dimensionin a range of from about 50 nanometers to about 500 nanometers. In anexemplary embodiment, FIG. 4 shows a micrograph 40 of a cross sectionalview of a nanotoughened cyanoethyl cellulose (CR-C) film 42. Themicrograph is a transmission electron micrograph. The micrograph of FIG.4 clearly shows nanostructures 44 of about 500 nm in their largestdimension, formed of the toughening material in the CR-C film 42.

Due in part to the formation of these toughening nanostructures, thecyanoresin dielectric film becomes flexible with good mechanicalstrength, which is essential for thin film development. Table 1 (below)shows tensile strength values for the nanotoughened CR-C dielectricfilms. Furthermore, these toughened cyanoresin films maintain theirexcellent dielectric properties, as shown in Table 2 (below). Thus,toughening of the cyanoresins enables thin film fabrication of thedielectric films with good mechanical strength.

According to the embodiments of the invention, the cyanoresin dielectricfilm may be improved by controlling the deposition conditions. Forexample, by performing the coating processes in a clean roomenvironment, high quality thin films may be obtained. The cyanoresinfilms processed by the above processes showed unexpectedly highbreakdown strength. In one embodiment, the cyanoresin dielectric filmhas a breakdown strength of at least about 300 kV/mm. In a particularembodiment, the cyanoresin dielectric film has a breakdown strength in arange from about 300 kV/mm to about 1000 kV/mm.

EXAMPLES Example 1

10 grams of cyanoethyl cellulose (CR-C resin) powder was added intoapproximately 90 grams of solvent to prepare a solution with about 10%polymer by weight. The solution was stirred at room temperature with amagnetic stirrer for two hours to dissolve the CR-C resin. A tougheningmaterial, M22 (20 wt % of CR-C resin) was added into the solution. TheM22 material was dissolved in the solution by a stirring process. Thesolution was then filtrated, using a 1-micron filter. The solution wasthen cast on a clean glass slide and dried at 100 degree Celsius for twohours. The toughened CR-C film was then peeled off from the glass slideand further dried in a vacuum oven overnight. Free-standing films ofthicknesses from about 5.5 microns and about 15 microns were cast.Dielectric breakdown strength was then measured, generally following theASTM D149 method. The top electrode and bottom electrodes were stainlesssteel plates. The film was immersed in clean insulation mineral oil, anddirect current (DC) voltage was applied at a ramp rate of 500 V/s, untilthe sample failed. The dielectric breakdown strengths of nanotoughenedCR-C films were found to be 400 kV/mm for a 5.5 micron-thick film, and570 kV/mm for a 15 micron-thick film.

Example 2

CR-C films toughened with 5 wt %, 10 wt % and 20 wt % M22, each of about12 micron thickness, were cast by the same process as discussed above inexample 1. The tensile strength of each of the film was measured. Table1 shows improved tensile strength of each of the nanotoughened CR-C(CR-C neat) films as compared to non-toughened CR-C film.

TABLE 1 Tensile strength of nanotoughened cyanoethyl cellulose (CR-C)films Cyanoresin Tensile Strength Dielectric Film (ksi) CR-C neat 5.4CR-C + 5% M22  6.2 CR-C + 10% M22 5.9 CR-C + 20% M22 5.9

Example 3

Nanotoughened CR-C dielectric films toughened with a differenttoughening material, M22, M22N, STM1700 (a siloxane polyetherimide blockcopolymer from SABIC) and BTDA-ODA/PDA (polyimide) of about 20 wt % ofCRC resin were cast by the process as described above in example 1.Table 2 shows the dielectric constant of each film, along withnon-toughened CR-C (CR-C neat) film. It is clear from the data thatthere is no substantial change in the dielectric constant, upontoughening the CR-C resin with the toughening materials.

TABLE 2 Dielectric constant of nanotoughened cyanoethyl cellulose (CR-C)films Cyanoresin Dielectric Dielectric Film Constant at 1 kHz CR-C neat16.6 CR-C + M22 13.4 CR-C + M22N 14.4 CR-C + STM1700 18.3 CR-C +BTDA-ODA/PDA 13.8

While only certain features of the invention have been illustrated anddescribed herein, many modifications and changes will occur to thoseskilled in the art. It is, therefore, to be understood that the appendedclaims are intended to cover all such modifications and changes as fallwithin the true spirit of the invention.

1. An article, comprising a cyanoresin dielectric film, wherein thecyanoresin dielectric film comprises nanostructures of a tougheningmaterial.
 2. The article of claim 1, wherein the cyanoresin dielectricfilm comprises at least one cyanoresin selected from the groupconsisting of cyanoethyl pullulan, cyanoethyl polyvinylalchohol,cyanoethyl hydroxyethyl cellulose, cyanoethyl cellulose or a combinationthereof.
 3. The article of claim 1, wherein the toughening materialcomprises a thermoplastic polymer.
 4. The article of claim 3, whereinthe thermoplastic polymer comprises an acrylate block copolymer.
 5. Thearticle of claim 3, wherein the thermoplastic polymer comprises aromaticpolyimides formed from poly(amic-acids).
 6. The article of claim 1,wherein the cyanoresin dielectric film comprises at least about 10% byweight of the toughening material.
 7. The article of claim 1, whereinthe cyanoresin dielectric film has a thickness in a range from about 0.1micron to about 50 microns.
 8. The article of claim 7, wherein thecyanoresin dielectric film has a thickness in a range from about 0.1micron to about 10 microns.
 9. The article of claim 1, wherein thetoughening material is dispersed within the cyanoresin.
 10. The articleof claim 1, wherein the cyanoresin dielectric film further comprisesfiller particles dispersed in the cyanoresin.
 11. The article of claim10, wherein the filler particles comprise a ceramic.
 12. The article ofclaim 11, wherein the filler particles comprise a ferroelectric or anantiferroelectric material.
 13. The article of claim 12, wherein thefiller particles are oriented parallel to an electric field.
 14. Thearticle of claim 13, wherein the electric field aligns the particles ina columnar structure.
 15. The article of claim 10, wherein the meanparticle size of the filler particles is in a range from about 5nanometers to about 200 nanometers.
 16. The article of claim 15, whereinthe mean particle size of the filler particles is in a range from about5 nanometers to about 100 nanometers.
 17. The article of claim 1,wherein the cyanoresin dielectric film has a breakdown strength in arange from about 200 kV/mm to about 1000 kV/mm.
 18. The article of claim17, wherein the cyanoresin dielectric film has a breakdown strength in arange from about 400 kV/mm to about 700 kV/mm.
 19. The article of claim1, wherein the cyanoresin dielectric film has a dissipation factor in arange from about 0.01 to about 0.1 at 1 kHz.
 20. The article of claim 1,wherein the cyanoresin dielectric film has a dielectric constant in arange from about 10 to about
 50. 21. The article of claim 20, whereinthe cyanoresin dielectric film has a dielectric constant in a range fromabout 10 to about
 20. 22. A capacitor, comprising: a cyanoresindielectric film; and at least one electrode coupled to the cyanoresindielectric film, wherein the cyanoresin dielectric film comprisesnanostructures of a toughening material.
 23. The capacitor of claim 22,having an energy density of at least about 5 J/cc.
 24. A method offorming a cyanoresin dielectric film, the method comprising the stepsof: dissolving a cyanoresin in a solvent to form a solution; dispersinga toughening material in the solution; and applying the solution to asubstrate to form the cyanoresin dielectric film, wherein the cyanoresindielectric film comprises nanostructures of the toughening material. 25.The method of claim 24, wherein the step of dispersing the tougheningmaterial is carried out by a melt dispersion technique or a solventdispersion technique.